Staphylococci are frequent human commensals and some species can cause disease. Staphylococcus aureus in particular is a dangerous human pathogen. In staphylococci, the ability to sense the bacterial ...cell density, or quorum, and to respond with genetic adaptations is due to one main system, which is called accessory gene regulator (Agr). The extracellular signal of Agr is a post-translationally modified peptide containing a thiolactone structure. Under conditions of high cell density, Agr is responsible for the increased expression of many toxins and degradative exoenzymes, and decreased expression of several colonization factors. This regulation is important for the timing of virulence factor expression during infection and the development of acute disease, while low activity of Agr is associated with chronic staphylococcal infections, such as those involving biofilm formation. Accordingly, drugs inhibiting Agr are being evaluated for their capacity to control acute forms of S. aureus infection.
Escherichia coli can survive improper disinfection processes, which is a potential source of contamination of food products. Benzalkonium chloride (BC) is a common disinfectant widely used in food ...industry. Bacterial quorum sensing (QS) plays a major role in food spoilage, biofilm formation and food-related pathogenesis. Understanding QS can help to control the growth of undesirable food-related bacteria. The LuxS/AI-2 QS system of E. coli has been confirmed to regulate many important phenotypes including biofilm formation and motility. In the current study, we aimed to investigate the effect of sublethal concentrations of BC on the LuxS/AI-2 system of E. coli isolates from retail meat samples, as well as bacterial biofilm formation and motility. Our results showed that sublethal concentrations of BC promoted AI-2 production in four test E. coli isolates. The results from microplate assay and confocal laser scanning microscopy (CLSM) analysis indicated that sublethal concentrations of BC enhanced biofilm formation of E. coli. When treated with sublethal concentrations of BC, exopolysaccharides (EPS) production during biofilm development increased significantly and swimming motility of tested isolates was also promoted. The expression levels of luxS, biofilm-associated genes and flagellar motility genes were increased by BC at sublethal concentrations. Our findings underline the importance of proper use of the disinfectant BC in food processing environments to control food contamination by E. coli.
•Sublethal concentrations of benzalkonium chloride (BC) promoted AI-2 production in E. coli.•Sublethal concentrations of BC enhanced biofilm formation of E. coli.•Sublethal concentrations of BC improved EPS production and swimming motility.•luxS, biofilm-, and flagellar-associated genes were upregulated when exposed to BC.
Serratia sp. cause food losses and waste due to spoilage; it is noteworthy that they represent a dominant population in seafood. The main spoilage associated species comprise S. liquefaciens, S. ...grimesii, S. proteamaculans and S. quinivorans, also known as S. liquefaciens-like strains. These species are difficult to discriminate since classical 16S rRNA gene-based sequences do not possess sufficient resolution. In this study, a phylogeny based on the short-length luxS gene was able to speciate 47 Serratia isolates from seafood, with S. proteamaculans being the main species from fresh salmon and tuna, cold-smoked salmon, and cooked shrimp while S. liquefaciens was only found in cold-smoked salmon.
The genome of the first S. proteamaculans strain isolated from the seafood matrix (CD3406 strain) was sequenced. Pangenome analyses of S. proteamaculans and S. liquefaciens indicated high adaptation potential. Biosynthetic pathways involved in antimicrobial compounds production and in the main seafood spoilage compounds were also identified. The genetic equipment highlighted in this study contributed to gain further insights into the predominance of Serratia in seafood products and their capacity to spoil.
•luxS sequencing allows reliable assignment of Serratia liquefaciens-like species.•S. proteamaculans and S. liquefaciens are preponderant in the seafood microbiome.•The genome of S. proteamaculans CD3406 from shrimp was sequenced.•Genetic traits were correlated to seafood adaptation and spoilage.
The quorum-sensing (QS) system is an intercellular cell-cell communication mechanism that controls the expression of genes involved in a variety of cellular processes and that plays critical roles in ...the adaption and survival of bacteria in their environment. The LuxS/AI-2 QS system, which uses AI-2 (autoinducer-2) as a signal molecule, has been identified in both Gram-negative and Gram-positive bacteria. As one of the important global regulatory networks in bacteria, it responds to fluctuations in the numbers of bacteria and regulates the expression of a number of genes, thus affecting cell behavior. We summarize here the known relationships between the LuxS/AI-2 system and drug resistance, discuss the inhibition of LuxS/AI-2 system as an approach to prevent bacterial resistance, and present new strategies for the treatment of drug-resistant pathogens.
Streptococcus gordonii is a commensal Gram‐positive bacterium that acts as an opportunistic pathogen that can cause apical periodontitis, endocarditis, and pneumonia. Biofilm formation of bacteria is ...important for the initiation and progression of such diseases. Although lipoproteins play key roles in physiological functions, the role of lipoproteins of S. gordonii in its biofilm formation has not been clearly understood. In this study, we investigated the role of lipoproteins of S. gordonii in the bacterial biofilm formation using its lipoprotein‐deficient strain (Δlgt). The S. gordonii Δlgt exhibited increased biofilm formation on the human dentin slices or on the polystyrene surfaces compared to the wild‐type strain, while its growth rate did not differ from that of the wild‐type. In addition, the S. gordonii Δlgt strain exhibited the enhanced LuxS mRNA expression and AI‐2 production, which is known to be a positive regulator of biofilm formation, compared to the wild‐type. Concordantly, the augmented biofilm formation of S. gordonii Δlgt was attenuated by an AI‐2 inhibitor, D‐ribose. In addition, lipoproteins from purified S. gordonii inhibited the biofilm formation of S. gordonii wild‐type and Δlgt. Taken together, these results suggest that lipoprotein‐deficient S. gordonii form biofilms more effectively than the wild‐type strain, which might be related to the AI‐2 quorum‐sensing system.
Escherichia coli is considered one of the uropathogenic bacteria with different infection symptoms representing mild illness to acute sepsis. This study aims to detect E. coli in patients with ...urinary infection and investigate quorum sensing genes (lux S and motA) in multi-drug resistant isolates of E. coli. 200 urine samples were collected from patients with urinary tract infections from several hospitals in Baghdad. The antibiotics sensitivity test showed high resistance of isolates for Ampicillin (100%), Cefazolin (97%), Trimethoprim/ Sulfamethoxazole (83%), Ceftriaxone (77%), Ceftazidime and Ciprofloxacin (70% each of them), and moderate resistance of isolates for Levofloxacin (50%), Gentamicin (47%), Cefepime (40%), while low resistance Piperacillin/ Tazobactam (33%), Cefoxitin (30%), Nitrofurantoin (17%), Imipenem (10%), Ertapenem and Amikacin (7% each of them), and Tigecycline (3%). The results showed an increase percentage of infection in females was 30% in the ages 30-44 years, whereas in ages 15-29 and more than 45 years was 17%. There was a high percentage (57.11%) of resistant isolates in females which are ages 30-44 years. While the ages more than 45 years were 66.4% and ages 15-29 were 34%. While, in males, the percentage was high in ages more than 45 years (35.25%) followed by age groups 30-44 years (31.5%) and 15-29 years (31%). The prevalence percentage for luxS and motA genes in E. coli was 100%. In conclusion, E. coli isolates were multi-drug resistant due to all isolates had quorum sensing genes. Moreover, uropathogenic of E. coli in females was more frequent than in males due to the resistance of bacteria to antibiotics.
This study illustrated the texture changes of
Shewanella baltica
-inoculated
Litopenaeus vannamei
during refrigerated storage with the exogenous addition of
Lactobacillus plantarum
SS-128. The group ...inoculated with SS-128 had an improved texture compared with that inoculated with the
luxS
-mutant group (Δ
luxS
). Proteomics were conducted to analyze the protein alterations in
L. vannamei
and supernatant, respectively. During storage, many texture-related proteins, including myosin heavy chain and beta-actin, were maintained due to
luxS
. Some endogenous enzymes related to the energy metabolism and hydrolysis of
L. vannamei
were downregulated. The
luxS
-induced interaction with
S. baltica
showed significant changes in the expression of some critical enzymes and pathways. The ATP-dependent zinc metalloprotease FtsH and protease subunit HslV were downregulated, and the oxidative phosphorylation and glycosaminoglycan degradation pathways in
S. baltica
were inhibited, resulting in the slow deterioration of
L. vannamei
. By exploring the mechanism underlying SS-128-led manipulation of the metabolism of spoilage bacteria, we clarified the texture maintenance mechanism of
luxS
in SS-128, providing theoretical evidence for SS-128 application in food preservation.
Cronobacter spp. are high acid resistance pathogens classified as Class A pathogens in powdered infant formula. Herein, we investigated the function of Cronobacter luxS in acid response. Results ...showed that luxS significantly increased the resistance to acid, demonstrating bacterial survival, bacterial morphology and biofilm formation. Furthermore, LuxS might enhance acid response by mediating the up‐regulation of 5‐methyltetrahydropteroyltriglutamate–homocysteine S‐methyltransferase and homocysteine S‐methyltransferase and the down‐regulation of methionine adenosyltransferase in the quorum sensing pathway. Therefore, the quorum sensing pathway mediated by luxS is the key control target for Cronobacter survival in acidic environments.
Our study showed that luxS significantly increased the resisitance to acid, demonstrating in bacterial survival, bacterial morphology and biofilm formation. Quorum sensing pathway mediated by luxS is the key control target for Cronobacter survival in acidic environments, especially the essential factors metE, mmuM and metK.
The LuxS/AI-2 system of Streptococcus suis Wang, Yang; Wang, Yuxin; Sun, Liyun ...
Applied microbiology and biotechnology,
09/2018, Letnik:
102, Številka:
17
Journal Article
Recenzirano
Quorum sensing (QS) is an important protective mechanism that allows bacteria to adapt to its environment. A limited number of signal molecules play the key role of transmitting information in this ...mechanism. Signals are transmitted between individual bacterium through QS systems, resulting in the expression of specific genes. QS plays an important role in a variety of bacterial processes, including drug resistance, biofilm formation, motility, adherence, and virulence. Most Gram-positive and Gram-negative bacteria possess QS systems, mainly the LuxS/AI-2-mediated QS system. Evidence has been brought that LuxS/AI-2 system controls major virulence determinants in
Streptococcus suis
and, as such, the ability of this bacterial species to cause infections in humans and pigs. Understanding the
S. suis
LuxS/AI-2 system may open up novel avenues for decreasing the drug resistance and infectivity of
S. suis
. This article focuses on the progress made to date on the
S. suis
LuxS/AI-2-mediated QS system.
Cronobacter malonaticus
is a highly hyperosmotic‐resistant pathogen classified as Class A pathogen by the Food and Agriculture Organization of the United Nations (FAO). This study explored the roles ...of LuxS as a quorum‐sensing transcription factor in
C
.
malonaticus
to tolerate hyperosmotic stress, illustrating that LuxS contributed to survival, biofilm formation and reduced cellular injury when grown with 5.5% NaCl stress. Comparative proteomics between
C. malonaticus
WT and Δ
luxS
demonstrated that differentially expressed proteins (DEPs) were abundant in Fe‐S cluster proteins and oxidoreductases, suggesting a potential cross‐tolerance mediated by LuxS could contribute to resisting hyperosmotic stress. Herein, these findings will provide valuable information on LuxS‐mediated osmotic tolerance to controlling
C
.
malonaticus
contamination.
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